The invention pertains to raised floor panels used for clean rooms and the like.
Clean rooms are used mainly in semiconductor device manufacturing facilities to improve yield by reducing contamination due to causes such as airborne particles. The maximum particle count permissible in such clean rooms must meet very exacting requirements, and much effort is devoted to that end, including the use of a highly filtered airflow through the room and the use of a pressure differential between the room and the ambient. Typicall, filtered air enters the room through ceiling registers and exits through perforated floor panels forming a part of a raised (double) floor. The panels sit on adjustable height posts. The floor typically uses some perforated and some solid panels. Dampers or some other means can be used to regulate air flow. For example, a perforated panel can use a double layer of perforated sheet, and a movable register can be mounted between the two sheets to regulate airflow. The panels can comprise a metal pipe frame welded at the corners, on top of which is also welded, e.g. tack welded, a perforated metal sheet. Inside the frame, parallel to two of its sides, rectangular or L-shape cross bars are welded at their end to the other two sides and to the perforated sheet metal above.
One disadvantage of such raised floors is that once the panels are fabricated it is not convenient to change their size in the field if needed to fit a particular clean room. Another disadvantage is that the steel frame can rust and the covering can collect dirt, increasing the risk that the particle count in the clean room may exceed the permissible limit. Yet another disadvantage is that typically the airflow openings of such perforated panels comprise only about a quarter of the panel area.
In contrast, the invention provides panels which can be conveniently changed in size in the field, significantly reduce the risk of adverse effects on particle count, and can provide higher airflow per unit floor area. In one exemplary embodiment a panel in accordance with the invention comprises stainless steel tubes cut from tube stock, and a pair of spaced-apart, parallel spacer bars. Each spacer bar has a row of spacers facing the other spacer bar. One open end of a tube is slipped over a spacer of one spacer bar and the other open end of the same tube is slipped over the opposite spacer of the other spacer bar. No welding or adhesives are requried, and the size of a panel can be conveniently changed in the field by cutting different length tubes from tube stock, or by cutting parts or pre-cut tubes to make up a smaller panel. The spacer bars similarly can be cut in the field to reduce the other dimension of the panel. To facilitate assembly of a panel, the spacers can have chamfered guiding edges which make it easier to slip the open end of a tube over a spacer. To facilitate assembly of the panels into a raised floor, the longitudinal ends of the spacer bars have interlocks which secure the panels to each other. The bottom runs of the spacer bars have provisions for supporting movable registers (dampers) for regulating airflow, for example an L-shaped support flange on each spacer bar or a channel in the spacer bar. The tubes can be stainless steel or can be made of a carbon fiber material (electrically conductive). They can be round, or of rectangular cross section, or of some other cross section. The spacer bars can be made of a molded plastic material, preferably an electrically conductive material (for example a plastic material containing conductive fibers). The electrically conductive tubes and spacer bars are electrically grounded to reduce the chance that static electricity would adversely affect particle count.
Panels embodying the invention can be assembled conveniently in any size in the field or in the plant, show highly improved resistance to deterioration over time or due to corrosive chemicals and high airflow per unit area, lower the danger of contamination due to increased particle count, and can be conveniently replaced or reused as needed.